http://www.cnblogs.com/louyihang-loves-baiyan/p/4839869.html
http://www.cnblogs.com/louyihang-loves-baiyan/p/4885659.html?utm_source=tuicool&utm_medium=referral
http://blog.csdn.net/kuaitoukid/article/details/46740477
https://www.zhihu.com/question/27982282/answer/39350629
http://blog.csdn.net/yihaizhiyan/article/details/26484763
http://blog.csdn.net/kuaitoukid/article/details/46829355
http://blog.csdn.net/ttransposition/article/details/41806601 dpm